Methods and apparatus for facilitating concurrent push-to-talk over cellular (PoC) group communication sessions

ABSTRACT

Methods and apparatus for facilitating concurrent Push-to-talk over Cellular (PoC) group communication sessions for a mobile station ( 102 ) are disclosed. A first PoC communication session ( 550 ) for a first user group ( 504 ) is maintained while a second PoC communication session ( 552 ) for a second user group ( 506 ) is concurrently maintained, where the second user group ( 506 ) has at least one common member ( 516 ) with the first user group ( 504 ). The second user group ( 506 ) may have at least one member ( 518, 520 ) which is not included in the first user group ( 504 ). Through a user interface, a PoC user may select between the first and the second user groups ( 504  and  506 ) for communication or combine the communications. In an alternative embodiment, all of the members ( 518, 520, 522 ) of a second user group ( 604 ) may be included in a first user group ( 602 ). In a specific approach, encrypted data packets of a PoC communication sub-session are communicated during a PoC communication session. If a key for the encrypted data packets is known for the mobile station ( 102 ), the encrypted data packets are decrypted to facilitate the PoC communication sub-session involving the mobile station ( 102 ); otherwise the encrypted data packets are discarded.

BACKGROUND

1. Field of the Invention

The present invention relates generally to Push-to-talk over Cellular(PoC) communications, and more particularly to methods and apparatus forfacilitating concurrent PoC group communication sessions between mobilestations.

2. Description of the Related Art

A wireless communication device, such as a cellular telephone or mobilestation, is capable of making and receiving voice calls and/or sendingand receiving data over a wireless communication network. Recentdevelopments have given such mobile stations the ability to communicatein “push-to-talk” (PTT) modes using Push-to-talk over Cellular (PoC)technology. PoC communication utilizes Voice-over-IP (VoIP) techniqueswhich involve the communication of data packets carrying voiceinformation. PoC communication is adapted for one-to-one talks or grouptalks which are session-based.

The end user of a mobile station may send an “invitation” for PoCcommunication to other potential “participants” who may “accept” orignore the invitation. When an initiation is accepted, a PoC session iscreated between the two participants. Further acceptances of theinvitation will expand the session into a group session having more thantwo participants. When a participant is in one PoC group session,however, the participant may be invited into another PoC group sessionof a different group. To enter into the other PoC group session, theparticipant has to exit from the current PoC group session in order toaccept the other PoC group session. At least on some occasions, however,the participant may want to join the other PoC group session withoutdropping from the current PoC group session.

Accordingly, there is a resulting need for mobile station methods andapparatus for facilitating PoC group communication sessions thatovercome the deficiencies of the prior art.

SUMMARY

Methods and apparatus for facilitating concurrent Push-to-talk overCellular (PoC) group communication sessions are described herein. In oneillustrative example, a first PoC communication session for a first usergroup is maintained while a second PoC communication session for asecond user group is concurrently maintained, where the second usergroup has at least one common member with the first user group. Thesecond user group may also have at least one member which is notincluded in the first user group or, alternatively, all of the membersof the second user group may be included in the first user group.

A related method of processing PoC group communication sessions for amobile station involves maintaining a first PoC group communicationsession; receiving or sending an invitation into a second PoC groupcommunication session; and in response to an invitation acceptance intothe second PoC group communication session, facilitating theparticipation into the second PoC group communication session withoutterminating the first PoC group communication session.

In one specific approach for processing concurrent PoC sessions,encrypted data packets of a PoC communication sub-session arecommunicated during a PoC communication session. If a key for theencrypted data packets is known for a mobile station, the encrypted datapackets are decrypted to facilitate the PoC communication sub-session.Otherwise, the encrypted data packets are discarded. This approachfacilitates multiple concurrent talk groups for an end user despite onlya single PoC session being maintained by the network, to thereby savenetwork resources.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of present invention will now be described by way of examplewith reference to attached figures, wherein:

FIG. 1 is a block diagram which illustrates pertinent components of awireless communication network and a mobile station which communicateswithin this network, both configured to facilitate Push-to-talk overCellular (PoC) communications;

FIG. 2 is a more detailed diagram of the mobile station which maycommunicate within the wireless communication network;

FIG. 3 is a block diagram of system components pertaining to PoCcommunication sessions of the present application;

FIG. 4 is a flowchart which describes a general method of facilitatingconcurrent PoC group communication sessions between mobile stations;

FIG. 5 is a system diagram showing two concurrent PoC talk groups havingat least one common member and at least one uncommon member betweengroups;

FIG. 6 is a system diagram showing two concurrent PoC talk groups whereall members in one group are included within the other group;

FIG. 7 is a flowchart which describes a method of processing datapackets of concurrent PoC group communication sessions for mobilestations;

FIG. 8 is a flowchart which describes a specific technique forprocessing data packets of concurrent PoC group communication sessionsat a mobile station using encryption techniques; and

FIG. 9 is an illustration of information displayed in a visual displayof a mobile station for PoC session processing.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Methods and apparatus for facilitating concurrent Push-to-talk overCellular (PoC) group communication sessions are described herein. In oneexemplary method, a first PoC communication session for a first usergroup is maintained while a second PoC communication session for asecond user group is concurrently maintained, where the second usergroup has at least one common member with the first group. The seconduser group may also have at least one member which is not included inthe first user group or, alternatively, all of its members may beincluded in the first user group. Further details are described below.

FIG. 1 is a block diagram of a communication system 100 which includes amobile station 102 which communicates through a wireless communicationnetwork 104. Mobile station 102 preferably includes a visual display112, a keyboard 114, and perhaps one or more auxiliary user interfaces(UI) 116, each of which is coupled to a controller 106. Controller 106is also coupled to radio frequency (RF) transceiver circuitry 108 and anantenna 110.

Typically, controller 106 is embodied as a central processing unit (CPU)which runs operating system software in a memory component (not shown).Controller 106 will normally control overall operation of mobile station102, whereas signal processing operations associated with communicationfunctions are typically performed in RF transceiver circuitry 108.Controller 106 interfaces with device display 112 to display receivedinformation, stored information, user inputs, and the like. Keyboard114, which may be a telephone type keypad or full alphanumeric keyboard,is normally provided for entering data for storage in mobile station102, information for transmission to network 104, a telephone number toplace a telephone call, commands to be executed on mobile station 102,and possibly other or different user inputs.

Mobile station 102 sends communication signals to and receivescommunication signals from network 104 over a wireless link via antenna110. RF transceiver circuitry 108 performs functions similar to those ofa radio network (RN) 128, including for example modulation/demodulationand possibly encoding/decoding and encryption/decryption. It is alsocontemplated that RF transceiver circuitry 108 may perform certainfunctions in addition to those performed by RN 128. It will be apparentto those skilled in art that RF transceiver circuitry 108 will beadapted to particular wireless network or networks in which mobilestation 102 is intended to operate.

Mobile station 102 includes a battery interface 122 for receiving one ormore rechargeable batteries 124. Battery 124 provides electrical powerto electrical circuitry in mobile station 102, and battery interface 122provides for a mechanical and electrical connection for battery 124.Battery interface 122 is coupled to a regulator 126 which regulatespower to the device. When mobile station 102 is fully operational, an RFtransmitter of RF transceiver circuitry 108 is typically turned on onlywhen it is sending to network, and is otherwise turned off to conserveresources. Similarly, an RF receiver of RF transceiver circuitry 108 istypically periodically turned off to conserve power until it is neededto receive signals or information (if at all) during designated timeperiods.

Mobile station 102 operates using a memory module 120, such as aSubscriber Identity Module (SIM) or a Removable User Identity Module(R-UIM), which is connected to or inserted in mobile station 102 at aninterface 118. As an alternative to a SIM or an R-UIM, mobile station102 may operate based on configuration data programmed by a serviceprovider into an internal memory which is a non-volatile memory. Mobilestation 102 may consist of a single unit, such as a data communicationdevice, a cellular telephone, a multiple-function communication devicewith data and voice communication capabilities, a personal digitalassistant (PDA) enabled for wireless communication, or a computerincorporating an internal modem. Alternatively, mobile station 102 maybe a multiple-module unit comprising a plurality of separate components,including but in no way limited to a computer or other device connectedto a wireless modem. In particular, for example, in the mobile stationblock diagram of FIG. 1, RF transceiver circuitry 108 and antenna 110may be implemented as a radio modem unit that may be inserted into aport on a laptop computer. In this case, the laptop computer wouldinclude display 112, keyboard 114, and one or more auxiliary UIs 116,and controller 106 may remain within the radio modem unit thatcommunicates with the computer's CPU or be embodied as the computer'sCPU. It is also contemplated that a computer or other equipment notnormally capable of wireless communication may be adapted to connect toand effectively assume control of RF transceiver circuitry 108 andantenna 110 of a single-unit device such as one of those describedabove. Such a mobile station 102 may have a more particularimplementation as described later in relation to mobile station 202 ofFIG. 2.

Mobile station 102 communicates in and through wireless communicationnetwork 104. In the embodiment of FIG. 1, wireless network 104 is aThird Generation (3G) supported network based on Code Division MultipleAccess (CDMA) technologies. In particular, wireless network 104 is aCDMA2000 network which includes fixed network components coupled asshown in FIG. 1. Wireless network 104 of the CDMA2000-type includes aRadio Network (RN) 128, a Mobile Switching Center (MSC) 130, a SignalingSystem 7 (SS7) network 140, a Home Location Register/AuthenticationCenter (HLR/AC) 138, a Packet Data Serving Node (PDSN) 132, an IPnetwork 134, and a Remote Authentication Dial-In User Service (RADIUS)server 136. SS7 network 140 is communicatively coupled to a network 142(such as a Public Switched Telephone Network or PSTN), whereas IPnetwork is communicatively coupled to a network 144 (such as theInternet).

During operation, mobile station 102 communicates with RN 128 whichperforms functions such as call-setup, call processing, and mobilitymanagement. RN 128 includes a plurality of base station transceiversystems that provide wireless network coverage for a particular coveragearea commonly referred to as a “cell”. A given base station transceiversystem of RN 128, such as the one shown in FIG. 1, transmitscommunication signals to and receives communication signals from mobilestations within its cell. The base station transceiver system normallyperforms such functions as modulation and possibly encoding and/orencryption of signals to be transmitted to the mobile station inaccordance with particular, usually predetermined, communicationprotocols and parameters, under control of its controller. The basestation transceiver system similarly demodulates and possibly decodesand decrypts, if necessary, any communication signals received frommobile station 102 within its cell. Communication protocols andparameters may vary between different networks. For example, one networkmay employ a different modulation scheme and operate at differentfrequencies than other networks. The underlying services may also differbased on its particular protocol revision.

The wireless link shown in communication system 100 of FIG. 1 representsone or more different channels, typically different radio frequency (RF)channels, and associated protocols used between wireless network 104 andmobile station 102. An RF channel is a limited resource that must beconserved, typically due to limits in overall bandwidth and a limitedbattery power of mobile station 102. Those skilled in art willappreciate that a wireless network in actual practice may includehundreds of cells depending upon desired overall expanse of networkcoverage. All pertinent components may be connected by multiple switchesand routers (not shown), controlled by multiple network controllers.

For all mobile station's 102 registered with a network operator,permanent data (such as mobile station 102 user's profile) as well astemporary data (such as mobile station's 102 current location) arestored in a HLR/AC 138. In case of a voice call to mobile station 102,HLR/AC 138 is queried to determine the current location of mobilestation 102. A Visitor Location Register (VLR) of MSC 130 is responsiblefor a group of location areas and stores the data of those mobilestations that are currently in its area of responsibility. This includesparts of the permanent mobile station data that have been transmittedfrom HLR/AC 138 to the VLR for faster access. However, the VLR of MSC130 may also assign and store local data, such as temporaryidentifications. Mobile station 102 is also authenticated on systemaccess by HLR/AC 138. In order to provide packet data services to mobilestation 102 in a CDMA2000-based network, RN 128 communicates with PDSN132. PDSN 132 provides access to the Internet 144 (or intranets,Wireless Application Protocol (WAP) servers, etc.) through IP network134. PDSN 132 also provides foreign agent (FA) functionality in mobileIP networks as well as packet transport for virtual private networking.PDSN 132 has a range of IP addresses and performs IP address management,session maintenance, and optional caching. RADIUS server 136 isresponsible for performing functions related to authentication,authorization, and accounting (AAA) of packet data services, and may bereferred to as an AAA server.

Wireless communication network 104 also includes a Push-to-talk overCellular (PoC) server 137 which may be coupled to IP network 134. PoCserver 137 operates to facilitate PoC individual and group communicationsessions between mobile stations within network 104. A conventional PoCcommunication session involves a session connection between end users ofmobile stations, referred to as session “participants”, who communicateone at a time in a half-duplex manner much like conventionalwalkie-talkies or two-way radios.

Those skilled in art will appreciate that wireless network 104 may beconnected to other systems, possibly including other networks, notexplicitly shown in FIG. 1. A network will normally be transmitting atvery least some sort of paging and system information on an ongoingbasis, even if there is no actual packet data exchanged. Although thenetwork consists of many parts, these parts all work together to resultin certain behaviours at the wireless link.

FIG. 2 is a detailed block diagram of a preferred mobile station 202.Mobile station 202 is preferably a two-way communication device havingat least voice and advanced data communication capabilities, includingthe capability to communicate with other computer systems. Depending onthe functionality provided by mobile station 202, it may be referred toas a data messaging device, a two-way pager, a cellular telephone withdata messaging capabilities, a wireless Internet appliance, or a datacommunication device (with or without telephony capabilities). Mobilestation 202 may communicate with any one of a plurality of base stationtransceiver systems 200 within its geographic coverage area. Mobilestation 202 selects or helps select which one of base stationtransceiver systems 200 it will communicate with, as will be describedin more detail later in relation to FIGS. 3 and 4.

Mobile station 202 will normally incorporate a communication subsystem211, which includes a receiver 212, a transmitter 214, and associatedcomponents, such as one or more (preferably embedded or internal)antenna elements 216 and 218, local oscillators (LOs) 213, and aprocessing module such as a digital signal processor (DSP) 220.Communication subsystem 211 is analogous to RF transceiver circuitry 108and antenna 110 shown in FIG. 1. As will be apparent to those skilled infield of communications, particular design of communication subsystem211 depends on the communication network in which mobile station 202 isintended to operate.

Mobile station 202 may send and receive communication signals over thenetwork after required network registration or activation procedureshave been completed. Signals received by antenna 216 through the networkare input to receiver 212, which may perform such common receiverfunctions as signal amplification, frequency down conversion, filtering,channel selection, and like, and in example shown in FIG. 2,analog-to-digital (A/D) conversion. A/D conversion of a received signalallows more complex communication functions such as demodulation anddecoding to be performed in DSP 220. In a similar manner, signals to betransmitted are processed, including modulation and encoding, forexample, by DSP 220. These DSP-processed signals are input totransmitter 214 for digital-to-analog (D/A) conversion, frequency upconversion, filtering, amplification and transmission over communicationnetwork via antenna 218. DSP 220 not only processes communicationsignals, but also provides for receiver and transmitter control. Forexample, the gains applied to communication signals in receiver 212 andtransmitter 214 may be adaptively controlled through automatic gaincontrol algorithms implemented in DSP 220.

Network access is associated with a subscriber or user of mobile station202, and therefore mobile station 202 requires a memory module 262, suchas a Subscriber Identity Module or “SIM” card or a Removable UserIdentity Module (R-UIM), to be inserted in or connected to an interface264 of mobile station 202 in order to operate in the network.Alternatively, memory module 262 may be a non-volatile memory which isprogrammed with configuration data by a service provider so that mobilestation 202 may operate in the network. Since mobile station 202 is amobile battery-powered device, it also includes a battery interface 254for receiving one or more rechargeable batteries 256. Such a battery 256provides electrical power to most if not all electrical circuitry inmobile station 202, and battery interface 254 provides for a mechanicaland electrical connection for it. The battery interface 254 is coupledto a regulator (not shown in FIG. 2) which provides power V+ to all ofthe circuitry.

Mobile station 202 includes a microprocessor 238 (which is oneimplementation of controller 106 of FIG. 1) which controls overalloperation of mobile station 202. This control includes network selectiontechniques of the present application. Communication functions,including at least data and voice communications, are performed throughcommunication subsystem 211. Microprocessor 238 also interacts withadditional device subsystems such as a display 222, a flash memory 224,a random access memory (RAM) 226, auxiliary input/output (I/O)subsystems 228, a serial port 230, a keyboard 232, a speaker 234, amicrophone 236, a short-range communications subsystem 240, and anyother device subsystems generally designated at 242. Some of thesubsystems shown in FIG. 2 perform communication-related functions,whereas other subsystems may provide “resident” or on-device functions.Notably, some subsystems, such as keyboard 232 and display 222, forexample, may be used for both communication-related functions, such asentering a text message for transmission over a communication network,and device-resident functions such as a calculator or task list.Operating system software used by microprocessor 238 is preferablystored in a persistent store such as flash memory 224, which mayalternatively be a read-only memory (ROM) or similar storage element(not shown). Those skilled in the art will appreciate that the operatingsystem, specific device applications, or parts thereof, may betemporarily loaded into a volatile store such as RAM 226.

Microprocessor 238, in addition to its operating system functions,preferably enables execution of software applications on mobile station202. A predetermined set of applications which control basic deviceoperations, including at least data and voice communicationapplications, will normally be installed on mobile station 202 duringits manufacture. A preferred application that may be loaded onto mobilestation 202 may be a personal information manager (PIM) applicationhaving the ability to organize and manage data items relating to usersuch as, but not limited to, e-mail, calendar events, voice mails,appointments, and task items. Naturally, one or more memory stores areavailable on mobile station 202 and SIM 256 to facilitate storage of PIMdata items and other information.

The PIM application preferably has the ability to send and receive dataitems via the wireless network. In a preferred embodiment, PIM dataitems are seamlessly integrated, synchronized, and updated via thewireless network, with the mobile station user's corresponding dataitems stored and/or associated with a host computer system therebycreating a mirrored host computer on mobile station 202 with respect tosuch items. This is especially advantageous where the host computersystem is the mobile station user's office computer system. Additionalapplications may also be loaded onto mobile station 202 through network,an auxiliary I/O subsystem 228, serial port 230, short-rangecommunications subsystem 240, or any other suitable subsystem 242, andinstalled by a user in RAM 226 or preferably a non-volatile store (notshown) for execution by microprocessor 238. Such flexibility inapplication installation increases the functionality of mobile station202 and may provide enhanced on-device functions, communication-relatedfunctions, or both. For example, secure communication applications mayenable electronic commerce functions and other such financialtransactions to be performed using mobile station 202.

In a data communication mode, a received signal such as a text message,an e-mail message, or web page download will be processed bycommunication subsystem 211 and input to microprocessor 238.Microprocessor 238 will preferably further process the signal for outputto display 222 or alternatively to auxiliary I/O device 228. A user ofmobile station 202 may also compose data items, such as e-mail messages,for example, using keyboard 232 in conjunction with display 222 andpossibly auxiliary I/O device 228. Keyboard 232 is preferably a completealphanumeric keyboard and/or telephone-type keypad. These composed itemsmay be transmitted over a communication network through communicationsubsystem 211.

For voice communications, the overall operation of mobile station 202 issubstantially similar, except that the received signals would be outputto speaker 234 and signals for transmission would be generated bymicrophone 236. Alternative voice or audio I/O subsystems, such as avoice message recording subsystem, may also be implemented on mobilestation 202. Although voice or audio signal output is preferablyaccomplished primarily through speaker 234, display 222 may also be usedto provide an indication of the identity of a calling party, duration ofa voice call, or other voice call related information, as some examples.

Serial port 230 in FIG. 2 is normally implemented in a personal digitalassistant (PDA)-type communication device for which synchronization witha user's desktop computer is a desirable, albeit optional, component.Serial port 230 enables a user to set preferences through an externaldevice or software application and extends the capabilities of mobilestation 202 by providing for information or software downloads to mobilestation 202 other than through a wireless communication network. Thealternate download path may, for example, be used to load an encryptionkey onto mobile station 202 through a direct and thus reliable andtrusted connection to thereby provide secure device communication.

Short-range communications subsystem 240 of FIG. 2 is an additionaloptional component which provides for communication between mobilestation 202 and different systems or devices, which need not necessarilybe similar devices. For example, subsystem 240 may include an infrareddevice and associated circuits and components, or a Bluetooth™communication module to provide for communication with similarly-enabledsystems and devices. Bluetooth™ is a registered trademark of BluetoothSIG, Inc.

FIG. 3 is a block diagram of relevant system components 300 pertainingto Push-to-talk over Cellular (PoC) communications of the presentapplication. System components 300 include user equipment (UE) 302 whichrepresents a mobile station, a Push-to-talk over Cellular (PoC) server304, an access 306, a Group and List Management Server (GLMS) 308, an IPMultimedia Subsystem (IMS) core 312, and a presence server 310. Some ofthese components may be optional or not necessary for fundamentaloperation.

A PoC communication session is a session connection between end users ofa UE 302, referred to as session “participants”, who communicate one ata time in a half-duplex manner. PoC communication utilizes Voice over IP(VoIP) technology which involves the communication of data packetscarrying voice information. UE 302 is terminal equipment (e.g. a mobilestation) which includes PoC application client software, which includesfunctionality of the present application but otherwise utilizesconventional techniques. IMS core 312 includes a plurality of SessionInitiation Protocol (SIP) proxies and SIP registrars. The first point ofcontact for UE 302 is one of the proxies in IMS core 312 that isconfigured on UE 302 as the outbound proxy. In the IMS architecture, theoutbound proxy is known as the Proxy-CSCF (P-CSCF). IMS Core 312performs the following functions: (1) routing of SIP signaling betweenUE 302 and PoC server 304; (2) termination of SIP compression from UE302; (3) authentication and authorization; (4) maintenance of theregistration state and the SIP session state; and (5) reporting to thecharging system. UE 302 sends all its SIP messages to the IP address ofthe outbound proxy after resolving the SIP Uniform Resource Identifier(URI) of the outbound proxy to an IP address.

End users use GLMS 308 to manage groups, contact lists, and accesslists. A contact list is a type of address book that may be used by endusers to establish an instant talk session with other PoC users or PoCGroups. An end user may have one or several contact lists includingidentities of other PoC users or PoC groups. Contact list managementincludes operations to allow UE 302 to store and retrieve the contactlists located in GLMS 308. End users can define PoC groups. An end usermay select one group from the list to initiate an instant group talksession or a chat group talk session, depending on the type of group. Anaccess list is used by the end user as a means of controlling who isallowed to initiate instant talk sessions to the end user. An accesslist contains end user defined identities of other end users or groups.The end user may have one blocked identities list and one grantedidentities list.

PoC server 304 includes functionality to perform the PoC service. PoCServer 304 typically performs functions such as: (1) end-point for SIPsignaling; (2) end-point for real-time transport protocol (RTP) and RTPControl Protocol (RTCP) signaling; (3) SIP session handling; (4) policycontrol for access to groups; (5) group session handling; (6) accesscontrol; (7) do-not-disturb functionality; (8) floor controlfunctionality (floor control is a control mechanism that arbitratesrequests, from the UEs, for the right to speak); (9) talkeridentification; (10) participant information; (10) quality feedback;(11) charging reports; and (12) media distribution. Presence server 310manages presence information that is uploaded by presenceuser/network/external agents, and is responsible for combining thepresence-related information for a certain presentity from theinformation it receives from multiple sources into a single presencedocument.

An Is interface supports the communication between UE 302 and IMS core312. This communication includes SIP procedures which support the PoCfeatures. The protocol for the Is interface is Session InitiationProtocol (SIP). Is signaling is transported on User Datagram Protocol(UDP). The protocols over an If interface support the communicationbetween IMS core 312 and PoC server 304 for session control. Theprotocols over an It interface support the transport of talk bursts,floor control, and link quality messages between UE 302 and PoC Server304. The protocols over an Im interface support the communicationbetween UE 302 and GLMS 308 for the purpose of managing the groups,contact lists and access lists and Do-not-Disturb indication. HTTP/XMLprotocols are utilized for these purposes. The protocols over an Ikinterface support the communication between PoC Server 304 and GLMS 308,enabling PoC server 304 to retrieve the groups and access lists fromGLMS 308. The protocols over an Ips interface enable the uploading ofthe registration status from IMS core 312 to presence server 310 and thedissemination of the presence information between presence server 310and UE 302. The protocol over an Ipl interface enables the uploading ofDo-not-Disturb status and granted/blocked access lists from GLMS 308 topresence server 310. The group identity used on the Is interface betweenthe UE and IMS core for group talk is generated by GLMS 308.

Each entity in the PoC system is assigned one or more IP addressesbelonging to public or private IP realms. On the other hand, a end usermay address another user by a phone number. UE 302 sends a phone numberto IMS core 312 in a TEL Uniform Resource Locator (URL). The phonenumber may use the international E.164 format (prefixed with a ‘+’ sign)or a local format using a local dialing plan and prefix. IMS core 312interprets the phone number with a leading ‘+’ to be an E.164 number.Addressing by TEL URL for a PoC session requires that PoC Server 304 canresolve the TEL URL to a SIP URI, for instance by using DNS/ENUM orother local data base. A phone number in a local format is converted tothe E.164 format before DNS/ENUM is used.

End users may initiate PoC talk sessions. An INVITE request on the Isinterface contains an “Accept-Contact” header with a media feature tagindicating the PoC service. IMS core 312 is able to identify the requestas a PoC communication by inspecting the Accept-Contact header. ARequest-URI of the INVITE contains either the pre-configured ad-hocidentity (for instant personal talk and ad-hoc instant group) or a groupidentity (for instant group talk or chat group talk). Early sessionestablishment is used for having a session available for quickconnection establishment using “REFER”. The early sessionestablishment's INVITE does not have any referred party field and can bedifferentiated from this against other INVITEs. A transient groupidentity is generated by PoC server 304 and distributed to UE 302 in the“Contact” header. From an initiating UE 302, the public user identity ofthe inviting user is included in the “From” header. On the signalingtowards the invited user, the “From” header includes either the publicuser identity (instant personal talk, ad-hoc instant group) or the groupidentity (instant group talk or being added to a chat group).

Other than the inventive techniques described herein, the PoCarchitecture and signaling may be the same as is conventional asdescribed in current standard specifications such as Push-to-talk overCellular (PoC), Architecture, PoC Release 1.0—Architecture V1.1.0(2003-08) Technical Specification; and Push-to-talk over Cellular (PoC),Signaling Flows, PoC Release 1.0—Signaling Flows V1.1.3 (2003-08)Technical Specification.

Within the context of the architecture above, FIG. 4 is a flowchartwhich describes a general method of facilitating concurrent PoC groupcommunication sessions between mobile stations in accordance with thepresent application. This described method may be performed by a mobilestation (e.g. FIGS. 1 and 2) or a PoC server (e.g. FIGS. 1 and 3). Inaddition, the method may be embodied in a computer program product whichincludes a computer storage medium (e.g. computer disk or memory) andcomputer instructions stored in the computer storage medium.

Beginning at a start block 402 of FIG. 4, a first Push-to-talk overCellular (PoC) communication session between a first user group ismaintained (step 404). In addition, a second PoC communication sessionbetween a second user group is concurrently maintained, where the seconduser group has at least one common member with the first user group(step 406). For each different PoC group session, a separate session IDand group ID are maintained in memory in association with the otherpertinent session information. In a first embodiment relating to FIG. 4,the second user group has at least one member which is not included inthe first user group (described later below in relation to FIG. 5). In asecond embodiment relating to FIG. 4, all members of the second usergroup are included in the first user group (described later below inrelation to FIG. 6 as well as FIG. 7).

The second PoC communication session may be set up by a PoC user who isalready a participant in the first PoC communication session. In onescenario, the PoC user accepts an invitation to the second PoCcommunication session which was originated by another PoC user who mayor may not be a participant in the first PoC communication session. Inanother scenario, the PoC user of the first PoC communication sessionsends an invitation to one or more members of the second PoCcommunication session, which is accepted by at least one member of thesecond PoC communication session. As apparent, a related method ofprocessing PoC sessions in a mobile station involves maintaining a firstPoC group communication session; receiving or sending an invitation intoa second PoC group communication session during the first PoC groupcommunication session; and in response to an invitation acceptance intothe second PoC group communication session, facilitating theparticipation into the second PoC group communication session withoutterminating the first PoC group communication session.

As will be described in more detail below, the PoC sessions may beprocessed in either a combined or separate manner. If combinedprocessing is utilized, then the mobile station processes and outputsaudible signals from both PoC sessions simultaneously. If separateprocessing is utilized, then the mobile station processes and outputsaudible signals from only a single PoC session at a given time. Themanner in which the sessions are processed may be predetermined andfixed. That is, only combined PoC session processing or only supportseparate PoC session processing may be supported. Alternatively, bothtypes of PoC session processing may be supported where only one type ofprocessing is utilized at a given time as selected by the end user atuser interface.

One of two different ways to facilitate such session processing may beutilized. One approach is at the mobile station and the other approachis at the PoC server. The former approach may be more straightforward toimplement but may utilize additional radio resources compared to thelatter approach. If the mobile station approach is utilized, the PoCserver sends data packets from all possible group sessions in which themobile station may participate. The PoC user of the mobile stationselects, at the user interface, which session should be heard at themobile station or whether the group sessions should be combined. Inresponse, the mobile station processes the data packets in the combinedor separate manner accordingly. The selection by the PoC user at theuser interface may be performed at any time to change the PoC sessionconfiguration. Whenever the PoC user selects a new session configurationat the user interface, the mobile station changes in the PoC sessionprocessing accordingly.

If the PoC server approach is utilized, the mobile station sends aninstruction message to the PoC server in response to user inputcorresponding to which session should be heard at the mobile station orwhether the group sessions should be combined. Based on the decisionsmade at the user interface of the mobile station, the PoC serveraccordingly selects data packets of the chosen PoC group session orcombines audio signals of data packets from multiple PoC group sessions,and causes the resulting/selected data packets to be sent to the mobilestation through a single channel. Data packets associated with an unusedor discarded session is discarded at the PoC server and not sentover-the-air. The selection by the end user at the user interface may beperformed at any time to change the PoC session configuration. Wheneverthe PoC user selects a new session configuration at the user interface,the mobile station sends a new instruction to the PoC server to requesta change in the session configuration.

In addition to choosing what group session to listen to, a PoC user mayalso select which group session to speak to or whether to combinesessions. Such decisions may similarly be made at the user interface ofthe mobile station. Transmitted data packets may have a field whichidentifies the session ID of the associated PoC group session so thatthey may be processed accordingly.

FIG. 5 is a system diagram 500 showing two concurrent PoC talk groups504 and 506 utilizing the same PoC server 304. PoC talk group 504includes mobile stations 510, 512, 514, and 516 of a PoC group sessionS1 550 facilitated by PoC server 304. On the other hand, PoC talk group506 includes mobile stations 516, 518, and 520 of a PoC group session S2552 facilitated by PoC server 304. Thus, PoC talk groups 504 and 506have at least one common member 516. In this scenario, PoC talk groups504 and 506 also have at least one uncommon member between groups. Inparticular, mobile stations 510, 512, and 514 of PoC talk group 504 arenot within PoC talk group 506 and mobile stations 518 and 520 of PoCtalk group 506 are not within PoC talk group 504. Thus, communicationprivacy is maintained within PoC talk group 504 and within PoC talkgroup 506, where mobile station 516 has communication for both sessions.

The techniques described earlier above will be further described inrelation to FIG. 5. The following discussion relates to peforming PoCsession processing at the mobile station (as opposed to at the PoCserver). Mobile station 516 of FIG. 5 may process received data packetsof both PoC communication sessions in either a combined or separatemanner. The manner in which the sessions are processed (i.e. combined orseparate) may be selected by the end user at the user interface ofmobile station 516. If the combined processing approach is performed bymobile station 516, mobile station 516 receives and processes datapackets from both PoC group sessions 504 and 506 substantiallysimultaneously and mixes the audio for combined output at its speaker.Here, the same PoC server 304 regularly sends mobile station 516 datapackets from two different PoC group sessions S1 and S2 substantially atthe same time. As an option, if mobile station 516 has stereo audiocapability it may provide voice signals of the two different PoC groupsessions S1 and S2 through the left and right speaker channels,respectively. If the separate processing approach is performed by mobilestation 516, mobile station 516 processes data packets from only one PoCgroup session at a time, discarding data packets from the other PoCgroup session. The single PoC group session which is heard may beselected by the end user at the user interface of mobile station 516.Again, this type of processing is similar in experience as placing atelephone call “on hold” to accept another telephone call, with theability to switch back and forth between calls.

On the other hand, PoC server 304 may perform the PoC session processinginstead of mobile station 516. That is, PoC server 304 may be operativeto process PoC group sessions S1 and S2 using either the combined orseparate approach. The manner in which the PoC communication sessionsare processed may be selected in response to an end user's selection atthe user interface of mobile station 516, which causes a processinginstruction message to be sent from mobile station 516 to PoC server304. If the combined processing approach is performed by PoC server 304,PoC server 304 receives and processes data packets from both PoC groupsessions S1 and S2 substantially simultaneously, mixes audio signals ofboth sessions, reconstructs data packets having the combined audio andsends them to mobile station 516. Mobile station 516 may generallyprocess the data packets as is conventional. Thus, PoC server 304 maysend mobile station 516 data packets which have mixed audio signals fromtwo different PoC group sessions S1 and S2. If the separate processingapproach is performed by PoC server 304, PoC server 304 processes datapackets from only one PoC group session at a time, discarding datapackets from the other PoC group session. The single PoC group sessionwhich is heard at mobile station 516 may be selected by the end user atthe user interface of mobile station 516, which causes a processinginstruction message to be sent from mobile station 516 to PoC server304. Again, this type of processing is similar in experience as placinga telephone call “on hold” to accept another telephone call, with theability to switch back and forth between calls.

FIG. 6 is a system diagram 600 showing two concurrent PoC talk groups602 and 604 where all members in one group 604 are included within theother group 602. PoC talk group 602 includes mobile stations 510, 512,514, 516, 518, and 520 of a PoC group session S1 650 facilitated by PoCserver 304. On the other hand, PoC talk group 604 includes mobilestations 516, 518, and 520 of a PoC group session S2 652 facilitated byPoC server 304. Thus, PoC talk groups 602 and 604 have at least onecommon member 516, 518, and 520, and in fact all members of PoC talkgroup 604 are included within PoC talk group 602. Thus, communicationprivacy is maintained within PoC talk group 604 where mobile stations516, 518, and 520 have the ability to communicate in both sessions. InFIG. 6, the mobile stations or PoC server may process data packets ofboth PoC communication sessions in a separate manner, as described inrelation to FIG. 5. Which session of FIG. 6 is heard may be selected bythe end user at the user interface. Further, the session configurationof FIG. 6 may be implemented utilizing the techniques described below inrelation to FIG. 8.

FIG. 7 is a flowchart which describes a method of processing datapackets of concurrent PoC group communication sessions at a mobilestation. Beginning at a start block 702 of FIG. 7, a mobile stationreceives data packets of a PoC group communication session (step 704).If the mobile station is currently maintaining no more than one PoCcommunication session as tested in step 706, then the flowchart leads tostep 712; otherwise two or more PoC group communication sessions arebeing maintained and the flowchart continues to step 708. Thedecision-making in step 706 may be performed by identifying relevantsession data which is maintained in memory of the mobile station. If twoor more different sets of session data are stored (i.e. with two or moredifferent session IDs and/or group IDs), for example, then two or morePoC group communication sessions are being maintained.

As described earlier above, a mobile station may process received datapackets of both PoC group communication sessions in either a combinedmanner or a separate manner. The manner in which the sessions areprocessed may be predetermined and fixed by mobile station operation.That is, the mobile station may support only combined session processingor only support separate session processing. Alternatively, the mobilestation may support both types of session processing where only one typeis utilized as selected by the end user at user interface. If thecombined session processing is utilized as identified at step 708, themobile station processes data packets from both PoC group sessionssubstantially simultaneously and combines/mixes these signals (step710).

If the separate session processing is utilized as identified at step708, the mobile station processes data packets from only one PoC groupsession at a time (step 716), discarding data packets from the other PoCgroup session. With separate session processing, the end user of themobile station can select between the different PoC group sessions atthe user interface. The user interface may be or include one or morekeys of a keypad and/or a mouse cursor and a visual display of themobile station (see discussion with respect to FIG. 9 below), asexamples. Again, this type of processing is similar in experience asplacing a telephone call “on hold” to accept another telephone call,with the ability to switch back and forth between calls.

Regardless of whether the concurrent PoC group sessions are handled inthe combined or separate manner, the mobile station outputs audiblevoice signals from its speaker for the PoC group session(s) (step 712).The flowchart ends at a finish block 714. Note that, with separatesession processing, audible voice signals are not heard at the speakerof the mobile station for the PoC group session associated with thediscarded data packets. Also note that the end user may also be able toselect which session in which to speak, or select one or all sessions inwhich to speak at the same time. The transmitted voice data packets mayshave a field to identify the intended session ID(s) for furtherprocessing.

Although the method of FIG. 7 describes PoC session processing at themobile station, the PoC session processing may be performed similarly bythe PoC server as described earlier above. If the PoC server performsthe method of FIG. 7, step 712 for “Outputting Voice Signals” isreplaced by the sending of data packets to the mobile station forfurther processing. Also, the PoC server may receive instructionmessages from the mobile station based on the end user's inputcorresponding to which PoC group session to select or whether to combinethe PoC group sessions.

FIG. 8 is a flowchart which describes a specific technique forprocessing data packets of concurrent PoC group communication sessionsat a mobile station, which involves the use of encryption techniqueswhere separate group sessions need not be maintained by the PoC server.This technique may especially be implemented for the sessionconfiguration described above in relation to FIG. 6. Beginning at astart block 802 of FIG. 8, a mobile station receives data packets of aPoC group communication session (step 804). The mobile stationidentifies whether these data packets are encrypted (step 806). Themobile station may determine this, for example, based on data whichexists in an encryption ID field of an incoming data packet. If the datapackets are not encrypted as identified in step 806, then the mobilestation processes the data packets normally for PoC group sessionprocessing (e.g. in accordance with steps 706-712 of FIG. 7). If thedata packets are encrypted as identified in step 806, then the mobilestation identifies whether it has a valid key for decrypting theencrypted data packets (step 808). The mobile station may determinethis, for example, based on the data which exists in the encryption IDfield of the data packet and any prestored encryption ID in its memory.If the mobile station does not have a valid key for decrypting the datapackets, then the mobile station discards the data packets (step 810).If the mobile station has the valid key (e.g. the data in the encryptionID field matches that of the prestored encryption ID in its memory) astested in step 808, the mobile station proceeds to decrypt the datapackets using the stored key (step 812). These decrypted data packetsare for a PoC group sub-session within the PoC group session (e.g. PoCtalk group 604 within PoC talk group 602 of FIG. 6). Next, the mobilestation proceeds to process the decrypted data packets for the PoC groupsub-session (step 814). For example, the mobile station may output audiosignals corresponding to the data packets at its speaker. The flowchartends at a finish block 816.

FIG. 9 is an illustration of information displayed in a visual display902 of a mobile station for PoC session processing. Note that GROUP 1and GROUP 2 sessions are being concurrently maintained. Visual display902 has display items 910, 912, and 914 which are utilized for selectingwhich PoC group session(s) to process and for indicating which PoC groupsession(s) is currently being processed. Display item 910 is forselecting/indicating the GROUP 1 session, display item 912 is forselecting/indicating the GROUP 2 session, and display item 914 is forselecting/indicating ALL group sessions. In FIG. 9, display item 910corresponding to the GROUP 1 session is highlighted for indicating thatthe GROUP 1 session (and not GROUP2) is currently being processed. Acursor 904 may be utilized along with one or more switches (keys,spin-wheel, etc.) of the mobile station for the end user selection ofPoC session processing. A display item 906 is for indicating anycurrently received PoC session invitations.

As apparent, all of the components and techniques as described areuseful in that an end user may invite, accept, and participate in atleast two PoC group sessions simultaneously. The end user no longer hasto exit from an existing PoC group session when interested in aninvitation into or the creation of a new PoC group session. The receivedaudible voice signals of both PoC group sessions may be processedseparately or mixed for the participation in some or all communicationsessions. The end user may select which type of processing should beutilized and which sessions to participate in at the user interface.

Final Comments. Methods and apparatus for facilitating concurrentPush-to-talk over Cellular (PoC) group communication sessions have beendescribed. A first PoC communication session for a first user group ismaintained while a second PoC communication session for a second usergroup is concurrently maintained. The second user group has at least onecommon member with the first group. The second user group may also haveat least one member which is not included in the first user group or,alternatively, all of its members may be included in the first usergroup. This method may be performed by a PoC server of a communicationnetwork or by a mobile station corresponding to the at least one commonmember. The method is embodied in a computer program product comprisinga computer storage medium and computer instructions stored in thecomputer storage medium.

A related method of processing PoC communication sessions comprises theacts of maintaining a first PoC group communication session; receivingan invitation into a second PoC group communication session; receiving auser input for accepting the invitation into the second PoC groupcommunication session; and in response to receiving the user input foraccepting the invitation into the second PoC group communicationsession, facilitating the participation into the second PoC groupcommunication session without terminating the first PoC groupcommunication session. Conversely, the method may include the acts ofmaintaining a first PoC group communication session; sending aninvitation into a second PoC group communication session during thefirst PoC group communication session; and in response to receiving aninvitation acceptance into the second PoC group communication session,facilitating the participation into the second PoC group communicationsession without terminating the first PoC group communication session.

In a specific approach, encrypted data packets of a PoC communicationsub-session are communicated during a PoC communication session. If akey for the encrypted data packets is known by a mobile station, theencrypted data packets are decrypted to facilitate the PoC communicationsub-session. Otherwise, the encrypted data packets are discarded. Thisapproach facilitates multiple concurrent talk groups for an end userdespite only a single PoC session being maintained by the network, tothereby save network resources.

The above-described embodiments of the present application are intendedto be examples only. Those of skill in the art may effect alterations,modifications and variations to the particular embodiments withoutdeparting from the scope of the application. The invention describedherein in the recited claims intends to cover and embrace all suchchanges in technology.

1. A method of facilitating Push-to-talk over Cellular (PoC)communication sessions between mobile stations adapted to communicatevia wireless signals in a wireless communication network, comprising:maintaining, via the wireless network, a first Push-to-talk overCellular (PoC) communication session between a first user group ofmobile stations; and maintaining, via the wireless network, a second PoCcommunication session between a second user group of mobile stationsconcurrently while maintaining the first PoC communication sessionbetween the first user group of mobile stations, where at least a firstmobile station is a common member with both the first user group and thesecond user group in the first and the second PoC communicationsessions, and the first user group of mobile stations has at least asecond mobile station which is a non-member of the second user groupoutside of the second PoC communication session.
 2. The method of claim1, wherein all members of the second user group are included in thefirst user group.
 3. The method of claim 1, being performed by a PoCserver.
 4. The method of claim 1, being performed by the first mobilestation which is the common member.
 5. The method of claim 1, whereinthe method is embodied in a computer program product comprising acomputer storage medium and computer instructions stored in the computerstorage medium.
 6. The method of claim 1, further comprising: prior toconcurrently maintaining the second PoC group communication session,receiving or sending an invitation for the second PoC groupcommunication session; and wherein the act of concurrently maintainingthe second PoC group communication session is in response to aninvitation acceptance to the second PoC group communication session. 7.The method of claim 1, further comprising: receiving data packets fromboth the first and the second PoC group communication sessions;receiving an end user selection for communications associated with onlyone of the first and the second PoC group communication sessions at atime; and in response to the end user selection, causing data packets ofonly the selected PoC group communication session to be processed foroutputting audible signals of only the selected PoC communicationsession.
 8. The method of claim 1, further comprising: receiving datapackets from both the first and the second PoC group communicationsessions; receiving an end user selection for communications with boththe first and the second PoC group communication sessions at the sametime; and in response to the end user selection, causing data packets ofboth the first and second PoC group communication sessions to beprocessed and mixing audio signals of both the first and second PoCgroup communication sessions for output at a mobile station.
 9. Themethod of claim 1, further comprising: receiving encrypted data packetsof the second PoC communication session; if a decryption key for theencrypted data packets for the second PoC communication session isknown, decrypting the encrypted data packets for the second PoCcommunication session; and if the decryption key of the encrypted datapackets for the second PoC communication session is unknown, refrainingfrom decrypting the encrypted data packets for the second PoCcommunication session.
 10. The method of claim 1, further comprising:visually displaying an indication which indicates which one of the firstand the second PoC group communication sessions is being processed forcommunications.
 11. A mobile station, comprising: a wireless transceiveroperative for communications using wireless signals via a wirelesscommunication network; one or more processors coupled to the wirelesstransceiver; the one or more processors being operative with use of thewireless transceiver to: maintain a first Push-to-talk over Cellular(PoC) communication session between a first user group of mobilestations; and maintain a second PoC communication session between asecond user group of mobile stations, concurrently while maintaining thefirst PoC communication session between the first user group of mobilestations, where the mobile station is a common member with both thefirst user group and the second user group in the first and the secondPoC communication sessions, the first user group of mobile stationshaving at least one mobile station which is a non-member of the seconduser group outside of the second PoC communication session.
 12. Themobile station of claim 11, wherein all members of the second user groupare included in the first user group.
 13. The mobile station of claim11, wherein the one or more processors are further operative to: priorto concurrently maintaining the second PoC group communication session,receive or send an invitation for the second PoC group communicationsession; and wherein concurrently maintaining the second PoC groupcommunication session is in response to an invitation acceptance to thesecond PoC group communication session.
 14. The mobile station of claim11, wherein the one or more processors are further operative to:receiving, via the wireless transceiver, data packets from both thefirst and the second PoC group communication sessions; receive an enduser selection for communications associated with only one of the firstand the second PoC group communication sessions at a time; and inresponse to the end user selection, cause data packets of only theselected PoC group communication session to be processed for outputtingaudible signals of only the selected PoC communication session.
 15. Themobile station of claim 11, wherein the one or more processors arefurther operative to: receiving, via the wireless transceiver, datapackets from both the first and the second PoC group communicationsessions; receive an end user selection for communications with both thefirst and the second PoC group communication sessions at the same time;and in response to the end user selection, cause the data packets ofboth the first and second PoC group communication sessions to beprocessed for outputting audible signals from both the first and thesecond PoC group communication sessions simultaneously.
 16. The mobilestation of 11, wherein the one or more processors are further operativeto: receive, via the wireless network, encrypted data packets of thesecond PoC communication session; decrypt-the encrypted data packets forthe second PoC communication session, if a decryption key for theencrypted data packets for the second PoC communication session isknown; and discard and refrain from decrypting the encrypted datapackets for the second PoC communication session, if the key of theencrypted data packets for the second PoC communication session isunknown.
 17. A Push-to-talk over Cellular (PoC) server of a wirelesscommunication network, comprising: one or more processors; memory;computer instructions stored in the memory; the one or more processorsbeing operative in accordance with the computer instructions tofacilitate Push-to-talk over Cellular (PoC) communication sessionsbetween mobile stations which are adapted to communicate via wirelesssignals in the wireless communication network by: maintaining a firstPush-to-talk over Cellular PoC communication session between a firstuser group of mobile stations; and maintaining a second PoCcommunication session between a second user group of mobile stations,concurrently while maintaining the first PoC communication sessionbetween the first group of mobile stations, where at least a firstmobile station is a common member with both the first user group and thesecond user group in the first and the second PoC communicationsessions, and the first user group of mobile stations has at least asecond mobile station which is a non-member of the second user groupoutside of the second PoC communication session.
 18. The PoC server ofclaim 17, wherein all members of the second user group are included inthe first user group.
 19. The PoC server of claim 17, furthercomprising: a first session ID corresponding to the first user groupstored in the memory; and a second session ID corresponding to thesecond user group stored in the memory.
 20. The PoC server of claim 17,wherein the one or more processors are further operative for: receivingdata packets from both the first and the second PoC group communicationsessions: receiving a selection for communications associated with onlyone of the first and the second PoC group communication sessions at atime; and in response to the selection, causing data packets of only theselected PoC group communication session to be processed forcommunications and discarding data packets of the other PoC groupcommunication session.
 21. The PoC server of claim 17, wherein the oneor more processors are further operative for: receiving data packetsfrom both the first and the second PoC group communication sessions;receiving a selection for communications with both the first and thesecond PoC group communication sessions at the same time; and inresponse to the selection, causing the data packets of both the firstand second PoC group communication sessions to be processed, mixingaudio signals of both the first and second PoC group communicationsessions, and sending data packets having the mixed audio signals to amobile station.
 22. The PoC server of claim 17, wherein the one or moreprocessors are further operative to: receiving encrypted data packets ofthe second PoC communication session.
 23. A method in a mobilecommunication device of processing group communication sessions whichare facilitated via a wireless communication network, the methodcomprising the acts of: maintaining, by the mobile device, a first groupcommunication session which is facilitated via the wireless network;receiving, at the mobile device via the wireless network, an invitationinto a second group communication session which is facilitated via thewireless network; sending, from the mobile device via the wirelessnetwork, an invitation acceptance which accepts the invitation into thesecond group communication session; in response to sending theinvitation acceptance, participating, by the mobile device, in thesecond group communication session without terminating the first groupcommunication session by: receiving, via the wireless network, datapackets from both the first and the second group communication sessions;and causing the data packets of both the first and second groupcommunication sessions to be processed for outputting, from the mobiledevice, audible signals of both the first and the second groupcommunication sessions simultaneously.
 24. The method of claim 23,wherein the first group communication session is a first Push-to-talkover Cellular (PoC) communication session and the second groupcommunication session is a second PoC communication session.
 25. Themethod of claim 23, wherein the first group communication session has afirst user group of mobile stations and the second group communicationsession has a second user group of mobile stations, and the first usergroup includes at least one mobile station which is a non-member of thesecond user group outside of the second communication session.
 26. Themethod of claim 23, further comprising: visually displayingidentifications of the first and the second group communication sessionsbeing processed for communications.